Andersons pediatric cardiology 785
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Abstract
Althoughusuallydescribedas“cortriatriatum,”noheartshavebeen
describedthusfarwiththreeatrialchambers.Thelesionsaccountedfor
usingthisterminologyhavedivisionofeithertherightorleftatrial
chambers.Divisionoftheleftatriumismuchmorecommon.Thisis
producedbypresenceofanobliquefibromuscularshelf,whichdividesthe
atriumintopulmonaryvenousandvestibularchambers.Theovalfossacan
relatetoeitherchamber,soshuntinginthepresenceofadeficientatrial
septum,orapatentovalforamen,canbetoeitherofthedivided
components.Divisionoftherightatriumisproducedbypersistencein
postnatallifeofthevalvesthatinterpose,duringdevelopment,betweenthe
systemicvenoussinusandtheremainderoftherightatrium.Thischapter
describestheanatomicfeatures,diagnosticfindings,andtherapeuticoptions
forthevariouslesionsproducingdivisionoftheatrialchambers.
Keywords
Cortriatriatumdexter;cortriatriatumsinister;Eustachianvalve;valvesof
systemicvenoussinus;dividingshelf
Introduction
Division,orpartitioning,ofoneoftheatrialchambersisararemalformation.
Severesymptoms,orevendeath,mayresultifthisconditionisuntreated.When
recognizedandtreatedsurgically,lifeexpectancyshouldbenormal.Eitherthe
morphologicallyrightorthemorphologicallyleftatriumcanbedividedby
fibromuscularpartitions.Clinicallysignificantdivisionofthemorphologically
leftatriumisbyfarthemostcommontype,andthemostimportant.Frequently
describedas“cortriatriatum,”heartshavingsuchlesionsdonot,infact,possess
threeatrialchambers.Itisthereforesimplertodescribedividedleftorright
atriums.1Despitetheirrarity,themalformationsaresufficientlywell
circumscribedanatomicallytowarranttheirownchapter.
DividedMorphologicallyLeftAtrium
MorphologyandMorphogenesis
Church2isusuallycreditedasbeingthefirsttodescribedivisionoftheleft
atrium,althoughBorst3coinedtheterm“cortriatriatum.”Subsequentsuggested
classificationshavenotallbeenrestrictedtocasesrepresentingcongenital
partitioningoftheleftatrium.Onesystem,forexample,includedexamplesof
totallyanomalouspulmonaryvenousconnectiontothecoronarysinus,together
withaneurysmsoftheatrialseptum.4ThesystemproposedbyThileniusand
colleagues,5whichrepresentsthelargestreview,includedrarecasesreported
withatresiaofthemouthofthecoronarysinus,alongwithexamplesof
anomalouspulmonaryvenousconnectiontoamidlineadditionalchamber,which
thendrainedtothemorphologicallyrightatrium.Almostallcasesencountered
inclinicalpracticewillbeofthe“classic”type,withintracavitarydivisionofthe
leftatrium.Thisanomaly,alsocalled“cortriatriatumsinister,”isthefocusof
thischapter.
Inthetypicallesion,anobliquelyorientatedfibromuscularpartitiondivides
themorphologicallyleftatriumintoacompartmentconnectedtothepulmonary
veins,andasecondcomponentincommunicationwiththeatrialappendageand
themitralvalvarvestibule(Fig.30.1).Thecomponentshavebeendescribedin
variousways,withtheterms“proximal”and“distal”themselvesbeingusedwith
oppositemeanings,accordingtothefashioninwhichtheyareperceived.Such
problemscanbecircumventedsimplybydescribingthepulmonaryvenousand
thevestibularcomponents.
